diff --git a/prism/src/bin/prism.cygwin b/prism/src/bin/prism.cygwin
index 159723a7..363f9090 100644
--- a/prism/src/bin/prism.cygwin
+++ b/prism/src/bin/prism.cygwin
@@ -17,6 +17,9 @@ if [ "$PRISM_JAVAMAXMEM" != "" ]; then
 		echo; echo "Error: Environment variable PRISM_JAVAMAXMEM is invalid."; exit
 	fi
 	PRISM_JAVAMAXMEM="-Xmx$PRISM_JAVAMAXMEM"
+else
+	# default
+	PRISM_JAVAMAXMEM="-Xmx512m"
 fi
 
 # Add PRISM to PATH
diff --git a/prism/src/bin/prism.darwin b/prism/src/bin/prism.darwin
index 69dde357..8e3c1ecf 100755
--- a/prism/src/bin/prism.darwin
+++ b/prism/src/bin/prism.darwin
@@ -17,6 +17,9 @@ if [ "$PRISM_JAVAMAXMEM" != "" ]; then
 		echo; echo "Error: Environment variable PRISM_JAVAMAXMEM is invalid."; exit
 	fi
 	PRISM_JAVAMAXMEM="-Xmx$PRISM_JAVAMAXMEM"
+else
+	# default
+	PRISM_JAVAMAXMEM="-Xmx512m"
 fi
 
 # Add PRISM to DYLD_LIBRARY_PATH
diff --git a/prism/src/bin/prism.linux b/prism/src/bin/prism.linux
index 7062545b..b4fb240c 100755
--- a/prism/src/bin/prism.linux
+++ b/prism/src/bin/prism.linux
@@ -17,6 +17,9 @@ if [ "$PRISM_JAVAMAXMEM" != "" ]; then
 		echo; echo "Error: Environment variable PRISM_JAVAMAXMEM is invalid."; exit
 	fi
 	PRISM_JAVAMAXMEM="-Xmx$PRISM_JAVAMAXMEM"
+else
+	# default
+	PRISM_JAVAMAXMEM="-Xmx512m"
 fi
 
 # Add PRISM to LD_LIBRARY_PATH